Steam power plants generally comprise a steam turbine and a boiler, wherein a steam line is designed and arranged such that steam generated in the boiler can flow to the steam turbine. The boiler can produce steam with a temperature of greater than 600° C. and a pressure of greater than 300 bar. Such high steam temperatures and pressures present a challenge to the valves arranged in the steam lines. In general, two valves, specifically a quick-closing valve and a control valve, are arranged in a steam line in which steam is conveyed to a steam turbine. The quick-closing valve is provided for quick closing in the event of a fault and is accordingly designed for this case. The control valve takes on the task of regulating or controlling the supply of steam through the steam line when the quick-closing valve is open.
In modern steam power plants, both quick-closing valves and control valves consist essentially of a valve housing and a valve cone, wherein the valve cone is able to move, by means of a valve stem, in one direction. Steam can flow between the valve stem and the valve housing, wherein this flow is a leakage flow and is therefore termed valve-stem leakage steam. The valve-stem leakage steam is generally collected and supplied to the steam power plant as seal steam.
The high temperatures and high pressures of the steam meant that, hitherto, no other use was possible. Introducing the valve-stem leakage steam for example directly into a condenser would not be possible since, under certain operating conditions, air is drawn into the valve and could therefore lead to possible damage in the valve.